White Paper Supplement Rev. 0 Radon Emission from Feed Materials Production Center K-65 Silos November 28, 2014

Page 1 of 3

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the 

ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their 

technical support and review contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical 

issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy 

Act 5 USC §552a and has been cleared for distribution.

White Paper Supplement to Radon 

Emissions from Feed Materials Production 

Center K-65 Silos

Rev. 0

National Institute for Occupational 

Safety and Health 

November 28, 2014

Stuart L. Hinnefeld, Director

Division of Compensation Analysis and Support
White Paper Supplement Rev. 0 Radon Emission from Feed Materials Production Center K-65 Silos November 28, 2014

Page 2 of 3

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the 

ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their 

technical support and review contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical 

issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy 

Act 5 USC §552a and has been cleared for distribution.

DISCUSSION

NIOSH wrote this supplement to address a specific issue raised in SCA-2010b. The issue is that the 

thermal expansion release model postulated by RAC may not account for all ventilation releases during 

the period 1979-1987. SCA postulates the Venturi effect of wind on the silo domes would contribute 

additional radon releases, beyond what is accounted for by the thermal expansion approach. SCA-2010b 

also points out that RAC-1995b discussed a ventilation release term in addition to the thermal expansion 

term, but ultimately did not include such a term.

For the sake of discussion, we will suppose that there was a non-trivial Venturi effect release for the 

years 1979-1987. The magnitude of the Venturi effect release is assumed to be equal to the thermal 

expansion release because Table P-6 of RAC-1993 indicates that the modeled radon releases underpredicted measured concentrations for a set of radon samplers by roughly a factor of 2 (model prediction 

averaged 0.44 of measured values).

Next we’ll consider what effect this increased ventilation release would have on the calculated amount 

of radon that diffused into the headspace from the K-65 residues. The effective removal rate of radon 

from the silo headspaces, λeff , is the sum of the removal rates for ventilation and diffusion and the radon 

decay constant. From the RAC-1995b estimate of release, those values are:

λven = 0.0297 d-1 

λdiff = 0.00477 d-1

λRn = 0.1813 d-1 

Therefore,

λeff = 0.21577 

A Venturi effect release equal to the thermal expansion release would mean that λven would be 0.0594 d-1 

and λeff would be 0.24547 d-1 . This represents a 13.8% increase in total removal rate, and therefore a 

13.8% increase in the diffusion of radon from the K-65 residues into the headspace. This value is still 

far below the diffusion rate that would be necessary to support the release estimates in SCA-2008.
White Paper Supplement Rev. 0 Radon Emission from Feed Materials Production Center K-65 Silos November 28, 2014

Page 3 of 3

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the 

ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their 

technical support and review contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical 

issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy 

Act 5 USC §552a and has been cleared for distribution.

REFERENCES

RAC-1993, “The Fernald Dosimetry Reconstruction Project, Task 4, Environmental Pathways – Models 

and Validation,” Killough, G.G., et. al., March 1993 (SRDB Ref ID 075602).

RAC-1995b, “The Fernald Dosimetry Reconstruction Project, Task 5, Review of Historic Data and 

Assessments for the FMPC,” Shleien, B., et. al., March 1995 (SRDB Ref ID 038043).

SCA-2010b, “A Second White Paper Addressing Enhanced Radon Releases from the K-65 Silos at the 

Fernald Site,” Behling, U. H., April 2010.